My hen died today. I feel horrible. Helpless really. I noticed yesterday that she seemed strange - her comb was a little purple and swollen. She was eating and drinking. When I was doing my chores this morning I found her-barely alive. She died shortly after that. I don't detect any other other differences in any of the others. How concerned should I be for the rest of the chickens.? How can I know what happened? It makes me sad.